Extracorporeal Blood Filter System

ABSTRACT

A blood filter system used for the sequential filtering of blood while actively removing air bubbles and debris comprising a filter housing with unique conical, or cylindrical shape, a flared inlet port, a unique up and down blood flow path, a multi-stage sequential filter assembly, an active air purge assembly and a unique downspout assembly with outlet port. The filter housing is adapted so that blood passes from the inlet port through the multi-stage sequential filter assembly to the outlet port following an up and down flow path, while its unique shape and angled filters effectively direct any air bubbles and debris up and out of the blood stream toward the active air purge assembly where they are removed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a blood filter system for use inconnection with the filtration of blood in medical devices such as butnot limited to extracorproreal circulation systems used duringcardiopulmonary support Procedures. The blood filter system hasparticular utility in connection with the sequential filtering of bloodwhile actively removing air bubbles and debris.

2. Description of the Prior Art

Blood filter systems for extracorporeal circulations are desirable foreliminating micro-bubble contamination and foreign particles from thepatient's systemic circulation. It is critical that during anycardiopulmonary support procedures, there are no free gases, or airbubbles present in the blood returning to the patient. It is alsocritical that blood contacts the least amount of foreign surfaces andcontains the least amount of dilution from the extracorporealcirculation system.

The use of blood filters is known in the prior art. For example: U.S.Pat. No. 4,572,724; U.S. Pat. No. 5,744,047; U.S. Pat. No. 5,540,841;U.S. Pat. No. 5,362,406; U.S. Pat. No. 5,258,127, and U.S. Pat. No.3,701,433.

While the above-described devices fulfill their respective objectivesand requirements, the aforementioned patents do not describe a bloodfilter system that allows the sequential filtering of blood whileactively removing air bubbles and debris.

Accordingly, the prior art for blood filter devices used inextracorporeal circulation systems utilizes a large volume chamber withan inlet and outlet, a single stage micro-pore screen filter placed at90 degree angles to the blood flow path and a large contact surface areato filter air bubbles and debris from the blood stream.

The large volume chamber provides a decrease in blood flow velocity asblood passes through the filter to allow more time for the buoyantforces of any air bubbles present to act, causing them to rise up andseparate from the blood stream.

Additionally, construction of the large volume chamber usually includesrounded walls that force the blood to flow in a circular motion tocreate centrifugal forces within the filter chamber. The centrifugalforces acting on the various elements of blood cause the more dense RedBlood Cell's to spread out along the filters outer wall, while lessdense particles such as air bubbles, accumulate at the chambers centerwhere a purge port is located for easy removal.

Moreover, placement of the single stage micro-pore screen filter at 90degree angles to the blood flow path as described in the prior artreduces filter efficiency and debris clearance from the filter housing.As air bubbles and debris strike the pleated single stage micro-porescreen head on at 90 degree angles to its flow path, they can becomeeffectively trapped between the pleats and held against the screen bythe force of the blood flowing through it. Also, the force of collisioncaused by the direct impact between air bubbles and the filter mediumplaced at right angles to its flow path promotes further micro-bubblegeneration as larger bubbles colliding with the screen break apart andincrease the amount of filtration required.

Finally, extracorporeal blood filters rely heavily on the principle thatdescribes the Bubble Point Pressure as a means to separate air bubblesfrom the blood stream. The Bubble Point Pressure is defined as theamount of pressure required to eject air across a wetted pore. As airbubbles cannot easily pass through a wetted pore, their passage isblocked by the filter screen, which separates them from blood flowexiting the filter unless there exists a sufficiently high pre-screenpressure to force them through. Air bubbles entering the filteraccumulate on the proximal surface of the micro-pore screen and obstructblood flow so as to cause a rise in pre-screen pressure within thefilter housing. As air bubble accumulation on the micro-pore screencontinues, the pre-screen pressure also continues to rise until suchtime that the Bubble Point Pressure is reached and air is ejected acrossthe wetted pore.

To avoid this, currently available blood filter systems make use of alarge micro-pore screen surface area to increase the number of poresavailable and thereby reduce the potential risk of reaching the BubblePoint Pressure. Increasing the number of available pores is usuallyaccomplished by tightly folding, or pleating extra screen filtermaterial into the filter housing. This large screen surface areacontributes negatively to blood handling as it constitutes the majorityof foreign surface available for blood contact activation and also setsthe requirement for a larger volume filter housing. Although theaddition of extra screen filter material helps reduce the possibility ofreaching the Bubble Point Pressure, it also makes the job of ensuringthe filter is properly de-aired in a timely fashion during priming moredifficult, creating a possible safety hazard for the patient.

In conclusion, the above mentioned disadvantages of the prior art arecounterproductive to blood filtration as they may promote the build-upand retention of air bubbles and debris on the micro-pore screen, reducefilter efficiency and exposes the patient to increased risk ofembolization.

The currently available single stage micro-pore screen filter asdescribed in the prior art is unable to effectively remove all airbubbles and debris from the extracorporeal blood flow. In addition tothe foreign surface contact activation and excessive dilution commonlyseen during extracorporeal circulations, inadequate filtration continuesto play a major role in the problems associated with cardiopulmonarysupport procedures. Furthermore, advancements in the science ofextracorporeal circulation will likely continue to increase demand onsystem components and their performance as a means of achieving improvedpatient outcomes. Therefore, a need exists for an improved blood filtersystem that can increase filter efficiency while decreasing the amountof foreign contact surface area and priming volume required. In thisregard, the present invention while departing from conventional conceptsand designs of the prior art, substantially fulfills this need andprovides an apparatus primarily developed for the sequential filteringof blood and active removal of air bubbles and debris duringextracorporeal circulations.

SUMMARY OF THE INVENTION

In contrast to the design limitations inherent in currently availablefilters for extracorporeal circulation, the present invention providesan improved blood filter system and method which has all the advantagesof the prior art and many novel features that result in a blood filterwhich is not anticipated, rendered obvious, suggested, or even impliedby the prior art either alone, or in any combination thereof.

The present invention describes a method that allows for the sequentialfiltering of blood while actively removing air bubbles and debris andcan include a filter housing with a unique conical, or cylindricalshape, a flared inlet port, a unique up and down blood flow path, amulti-stage sequential filter assembly, an active air purge assembly anda unique downspout assembly with outlet port. The filter housing isadapted so that blood passes from the inlet port through the multi-stagesequential filter assembly to the outlet port following an up and downflow path, while its unique shape and angled filters effectively directany air bubbles and debris up and out of the blood stream toward theactive air purge assembly where they are removed.

The above summary has outlined the more important features of thepresent invention so that it may be better understood and itscontribution to the art may be better appreciated. There are of courseadditional features of the invention that will be described further andwhich will form the subject matter of the claims attached.

Numerous objects, features and advantages of the present invention willbe readily apparent to those of ordinary skill in the art upon a reviewof the following detailed description and accompanying illustrations. Inthis respect, before explaining the preferred embodiments of the presentinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction andarrangement of its components set forth in the following descriptions,or illustrations. Also, it is to be understood that the terminology usedis for the purpose of description and should not be regarded aslimiting.

As such, those skilled in the art will appreciate the concept upon whichthis disclosure is based and that it may be readily utilized for thedesign of other structures, methods and systems for carrying out theseveral purposes of the present invention and that the claims should beregarded as including such equivalent constructions insofar as they donot depart from the spirit and scope of the present invention.

It is therefore an object of the present invention to provide a new andimproved blood filter system that has all of the advantages of the priorart blood filters and none of the disadvantages.

It is another object of the present invention to provide a new andimproved blood filter system that may be easily and efficientlymanufactured.

An even further object of the present invention is to provide a new andimproved blood filter system that has a low cost of manufacture andwhich accordingly may allow low prices of sale to the consuming public.

Still another object of the present invention is to provide a new bloodfilter system that provides in the apparatuses and methods of the priorart some of the advantages thereof, while simultaneously overcoming someof the disadvantages normally associated therewith.

Even still another object of the present invention is to provide a bloodfilter system for the sequential filtering of blood while activelyremoving air bubbles and debris from the blood stream. This allows for ablood filter system that can have a smaller micro-pore screen filtercontact surface area, reduced total device priming volume, unique shapedfilter housing, unique up and down blood flow path, unique multi-stagesequential filter assembly, unique angled placement of the filtermaterial within the blood flow, unique sweeping action of blood flow onthe angled filter material, reduced force of collision between airbubbles and the angled filter material, unique active air purgeassembly, unique methods of actively removing air bubbles from blood,unique built-in pressure relief valve, unique downspout assembly and aunique method of preventing the filter from becoming de-primed.

These objects together with other various features of novelty thatcharacterize the invention are pointed out with particularity in theclaims annexed to and forming a part of this disclosure. For a betterunderstanding of the invention, its operating advantages and specificobjects obtained by its uses, reference should be made to theaccompanying drawings that illustrate the preferred embodiments of thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is better understood when the following detaileddescription is referenced to the attached drawings wherein:

FIG. 1 is a schematic diagram showing the blood filter systemspositioned within an extracorporeal circuit in accordance with theprinciples of the present invention.

FIG. 2 is a perspective view of the blood filter system of the presentinvention.

FIG. 3 is a front view of the blood filter system of the presentinvention.

FIG. 4 is a top view of the blood filter system of the presentinvention.

FIG. 5 is a cross-sectional view of the blood filter system of thepresent invention taken along line 5 in FIG. 4.

FIG. 6 is a cross-sectional view of the blood filter system of thepresent invention taken along line 6 in FIG. 5.

FIG. 7 is a cross-sectional view of the blood filter system of thepresent invention taken along line 7 in FIG. 4.

FIG. 8 is a cutaway perspective view of the sequential filter assemblyof the blood filter system of the present invention.

FIG. 9 is a top view of an alternate embodiment of the blood filtersystem of the present invention.

FIG. 10 is a cross-sectional view of an alternate embodiment of theblood filter system of the present invention taken along line 10 of FIG.9

FIG. 11 is a cross-sectional view of an alternate embodiment of theblood filter system of the present invention taken along line 11 in FIG.10.

FIG. 12 is an exploded perspective view of an alternate embodiment ofthe sequential filter assembly of the present invention

The same reference numerals refer to the same parts throughout thevarious figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and particularly to FIGS. 1-12, thepreferred embodiments of the present invention are shown and generallydesignated by the reference numerals 10 and 100.

FIG. 1 illustrates the placement of the new and improved blood filtersystems 10 and 100 in an extracorporeal circuit used duringcardiopulmonary support procedures. One possible bypass circuit isdescribed herewith, but other bypass circuits can also utilize the bloodfilter systems 10 and 100. In FIG. 1, a pump 16 draws blood from thepatient 11 via tube 12 into blood filter system 100 where micro-bubbles,free gases and debris are removed before being pumped into anoxygenating device 13. The oxygenating device 13 removes carbon dioxidefrom the blood and introduces oxygen from an oxygen filter 14 and tube15. Blood in oxygenating device 13 is then pumped into blood filtersystem 10 through tube 17 where micro-bubbles, free gasses and debrisare further removed from the blood. Following filtration, bloodcontaining bubbles and debris is purged from blood filter system 10 backto reservoir 21 in tube 24, while filtered blood is returned to patient11 through tube 18. In the event that there is excess blood wheresurgery is being performed, it may be removed through tube 19 by pump 20and delivered to reservoir 21. The excess blood then flows fromreservoir 21 through tube 22 to another blood filter system 10 beforebeing routed back to the oxygenating device 13 through tube 23.Additional blood filter systems 10 and 100 can be placed throughout thebypass circuit in any of the drainage, or infusion tubes and is notlimited to what is illustrated in FIG. 1.

As best illustrated in FIGS. 2, 3, 4 and 5 blood filter system 10 canhave a filter housing 30 with rising inner wall 31, an inlet port 32, ainlet channel 33, a multi-stage sequential filter assembly 60, a purgeport 42, an active air purge assembly 40 and a downspout assembly 34.The filter housing 30 can have a generally conical configuration, butother cylindrical or non-cylindrical configurations can be used.

As shown in FIG. 5, the multi-stage sequential filter assembly 60 canconsist of a first stage filter 61, a second stage filter 70 and a thirdstage filter 80 all of which can rest on and be secured to each other,the rising inner wall 31 and filter retaining ring 41. The active airpurge assembly 40 can be positioned on top of filter housing 30 and mayconsist of a hydrophobic filter 48, a one-way valve 52, an air removalport 44 and a pressure monitoring port 45. The air removal port 44 mayfeature a tethered cap which can be moved to close air removal port 44.The downspout assembly 34 can consist of a large diameter funnel 38, amicro-pore screen disk 39, an outflow tube 37, a mounting plate 35 andan outlet port 36. The outflow tube 37 may extend down from the interiorof the filter housing 30 to connect the bottom of the large diameterfunnel 38 to the outlet port 36. The large diameter funnel 38 may beadapted to retain a disc-shaped micro-pore screen filter 39, whichprevents air bubbles and debris from entering the filters outflow tube37. The disk shaped micro-pore screen filter 39 may be placed within thelarge diameter funnel 38 so that it remains submerged within the fluidfilled downspout assembly at all times. A mounting plate 35 may bepositioned along the outflow tube 37 to facilitate the manipulation andsecuring of the blood filter system 10. The mounting plate 35 may beconfigured to be self-locking when placed into a mounting device notshown to secure blood filter system 10 while in use.

The multi-stage sequential filter assembly 60 forms the centerpiece ofthe present invention, representing its primary achievement over that ofthe prior art.

As illustrated in FIGS. 5, 6, 7 & 8, the multi-stage sequential filterassembly 60 consists of multiple angled micro-pore screen filters 61, 70& 80 positioned one after the other between the inlet and outlet portsto form in part a major advancement in blood filtration forextracorporeal circulation. Filters 61, 70 & 80 contain a smoothmicro-pore filter screens 62, 72 & 82 within support frames 64, 74 & 84.The filter support frames 64, 74 & 84 attach to one another viaattachment points 68, 78 & 88, which are designed to limit turbulence asblood flows over them. 044 As shown in FIGS. 6 & 7, filter retainingring 41 comprises defined openings 66, 76 & 86. The tops of filters 61,70 & 80 attach to the underside of filter retaining ring 41 so that theproximal outside surface of smooth micro-pore filter screens 62, 72 & 82are in fluid communication with defined openings 66, 76, & 86 of filterretaining ring 41.

Blood flow through filter system 10 passes through each filter stage 61,70 & 80 in sequence to multiply the barrier to air bubble and debristransfer, greatly improving blood filtration and filter efficiency. Aslong as the Bubble Point Pressure is not exceeded, the wetted pores offilter screens 62, 72 & 82 allow only blood to pass through whilepreventing the passage of air bubbles and debris. Any air bubbles anddebris within the blood are directed up along the outside proximalsmooth surface of filter 61 and up through defined opening 66 of filterretaining ring 41 toward purge port 42 where they are removed. In theevent that the Bubble Point Pressure is exceeded and air is ejectedacross the micro-pore filter screen 62 of filter 61, they are thendirected to flow up along the outside proximal surface of filter 70 andthrough defined opening 76 of filter retaining ring 41 toward purge port42 where they are removed. If the Bubble Point Pressure is againexceeded and air is ejected across the micro-pores of filter screen 72of filter 70, they are then directed to flow up along the outsideproximal surface of filter 80 and through defined opening 86 of filterretaining ring 41 toward purge port 42 where they are removed. If theBubble Point Pressure is again exceeded and air is ejected across themicro-pore filter screen 82 of filter 80, the buoyant bubbles then flowup due to the low fluid flow velocity at this point created by the largediameter funnel 38. The buoyant bubbles can then come in contact withhydrophobic filter 48 of active air purge assembly 40 where they areremoved.

Placement of the multi-stage sequential filters 61, 70 & 80 at anglesgreater than 90 degrees to the blood flow limits debris trapping andimproves its clearance by reducing contact friction between air bubbles,or debris and the angled filter material. Instead of being held againstthe screen by the force of blood flowing through it, micro-bubbles anddebris are more easily swept up along the smooth proximal surface of theangled filters 61, 70 & 80 and through defined openings 66, 76 & 86toward purge port 42 where they are removed. This unique sweeping actionkeeps the outside proximal surface of smooth micro-pore screens 62, 72 &82 free of debris, further enhancing air bubble clearance and filterefficiency.

The angled filters 61, 70 & 80 also help reduce micro-bubble generationwithin the filter housing by diminishing the acute angle of directimpact and force of collision between air bubbles and the smoothmicro-pore filter screens 62, 72 & 82. This reduced force of collisionlimits air bubble fragmentation to further improve filter efficiency andperformance.

The above-mentioned benefits of the multi-stage sequential filterassembly 60 together provide improved filter efficiency, better airbubble and debris clearance and reduced micro-bubble generation overthat of the prior art.

As shown in FIGS. 3 & 4, inlet port 32 forms a flared inlet channel 33which is used to decrease blood flow velocity and allow more time forthe buoyant forces of any air bubbles present to act. This pre-filterreduction in flow velocity initiates bubble separation from the bloodstream before entering the filter housing proper and reduces the numberof bubbles that come in contact with the outside proximal surface of thesmooth micro-pore screens 62, 72 & 82. In a similar way, FIG. 5 showsthe large diameter funnel 38 of downspout assembly 34 also used todecrease flow velocity and improve air bubble separation, but at thefilters center directly below the active air purge assembly 40 wherebubbles are more easily removed through hydrophobic filter 48. Thesefeatures together improve air bubble separation and reduce the numberthat come in contact with the outside proximal surface of micro-porefilter screens 62, 72 & 82 and further improve debris clearance andfilter efficiency.

As illustrated in FIGS. 3 & 5, blood entering the filter first flows upin a smooth circular motion between filter housing 30 and rising innerwall 31 to form the first part of a unique up and down flow path. Theunique up and down flow path of the present invention improves filterefficiency by augmenting the buoyant forces of air bubbles as they moveup in the blood stream toward the filters top. Air bubbles at thefilters top then pass through defined openings 66, 76 & 86 of filterretaining ring 41 toward purge port 42 where they are removed, while thefiltered blood exiting the multi-stage sequential filter assembly 60then enters the large diameter funnel 38 where it is directed slowlydown through outflow tube 37 and outlet port 36. This completes the upand down flow path which places the buoyant forces of air bubbles andthe blood flow exiting the filter in opposite directions of each otherto again greatly improve air bubble separation and filter efficiency.

Also shown in FIG. 5, purge port 42 located on top of filter housing 30and in fluid communication with the interior of filter system 10 formsthe upper most portion of the filter housing proper. The active airpurge assembly 40 directly above filter retaining ring 41 comprises ahydrophobic filter 48 at its base in fluid communication with theinterior of filter housing 30, a one-way valve 52 in fluid communicationwith the hydrophobic filter 48, an air removal port 44 and pressuremonitoring port 45 in fluid communication with the one-way valve 52 anda method to allow the active removal of air bubbles from blood.

FIG. 6 illustrates the filter retaining ring 41 and active air purgeassembly 40 at a level above the one-way valve 52. The one-way valve 52rests on top of support frame 54, preventing it from collapsing backinto the active air purge assembly 40 as well as the retrograde flow offree gases back into the blood stream.

As seen in FIG. 7, the hydrophobic filter 48 is attached to supportframe 50 not shown, which prevents it from becoming displaced or damagedwhen exposed to positive or negative pressures. The hydrophobic filter48 allows an increase in air bubble removal without increasing theamount of blood flow shunted away from the filters outlet port 36. Thelarge diameter of the active air purge assembly 40 and hydrophobicfilter 48 allows it to act as a pressure relief valve as any excess gaspressure entering through inlet port 32 is easily vented to atmosphere.

The hydrophobic filter 48 is adapted so that free gasses and not theblood within the filter comes in contact with the one-way valve 52. Airbubbles and debris within the blood flow which pass through the wettedpores of filter screens 62, 72 & 82 are directed into the active airpurge assembly 40 where they come in contact with the hydrophobic filter48. Air bubbles in contact with the hydrophobic filter 48 may beabsorbed passively, or may be actively pulled from the blood using asuction source attached to the air removal port 44. The use of suctionand the resulting negative pressure it creates above hydrophobic filter48 ensures an active and more rapid absorption of air bubbles from theblood to further improve filter efficiency. Once through hydrophobicfilter 48, free gases then cross the one-way valve 52 before beingvented to the atmosphere through air removal port 44. A pressuremonitoring port 45 is used to keep negative pressures within the activeair purge assembly 40 at safe limits and within a user-defined range.

Moreover, by improving filter efficiency and micro-bubble clearance, thepresent invention also greatly reduces the potential risk of reachingthe Bubble Point Pressure. This important feature results in a majoraccomplishment that in turn greatly reduces the need for large numbersof available wetted pores and thereby allows the use of a smallermicro-pore screen filter size to reduce the amount of foreign contactsurface area and priming volume required. Additionally, the smallerscreen surface area and lack of pleated filter material as described inthe present invention will also help improve ease of priming and therebypromote better patient safety.

Blood filter system 10 was designed so that the active air purgeassembly 40, downspout assembly 34 and hydrostatic pressure containedwithin an extracorporeal circuit work in unison to prevent the filterfrom becoming de-primed. To achieve this the active air purge assembly40 at the filters top is designed to have a larger diameter opening thenthe inlet port 32 at the filters base, while the downspout assembly 34,which forms a sort of chamber at the filters center, is designed toretain hydrostatic pressure contained within the system to keep it fluidfilled while in use. More specifically, the filters outlet port 34 isconnected to the patient's circulation by way of tubing 17, or 22 asillustrated in FIG. 1. The result of this connection is that tubing 17,or 22 and downspout assembly 34 contain a hydrostatic pressure equal tothe height difference between the patient's heart (tubing connectionpoint) and the top of filters downspout assembly 34 (usually 25 to 30cmH2O). If a sufficient volume of air were accidentally pumped intoblood filter system 10 through inlet port 32 so that the space betweenfilter housing 30 and rising inner wall 31 became air filled, the largerdiameter of the active air purge assembly 40 would allow at least anequal volume of air to escape through hydrophobic filter 48 and purgeport 42 to prevent air pressure within filter housing 30 from exceedingthe hydrostatic pressure contained within downspout assembly 34. Thus,the hydrostatic pressure contained within the downspout assembly 34ensures that the large diameter funnel 38, outflow tube 37, outlet port36 and patient connection tubing 17, or 22 remain fluid filled, whileexcess air entering through the filters inlet port 32 is vented offthrough the active air purge assembly 40 and purge port 42. This featureof the present invention is unique to extracorporeal blood filtrationdevices and marks a first for improved patient safety by greatlyreducing the risk of introducing gross air embolism to the patient.Together the above-mentioned achievements and features of the presentinvention combine to provide significant benefits over that of the priorart blood filters for extracorporeal circulations.

FIGS. 9 & 10 illustrate an alternate preferred embodiment of the presentinvention as blood filter system 100 and which comprises a filterhousing 110, a rising inner wall 111, an inlet port 112, an inletchannel 114, a multi-stage sequential filter assembly 120, an active airpurge assembly 140 and downspout assembly 115. The filter housing 110can have a generally cylindrical configuration, but other configurationscan also be used.

As shown in FIGS. 10, 11 & 12 the multi-stage sequential filter assembly120 can consist of a first stage filter 122, a second stage filter 128and a third stage filter 134 all of which can rest on and be secured toeach other, the rising inner wall 111 and bottom surface of the filterretaining ring 153. The active air purge assembly 140 can be positionedon top of filter housing 110 and may consist of inlet openings 154, 156& 158, a purge port 150, a hydrophobic filter 144, a one-way valve 146,an air removal port 142 and a pressure monitoring port 148. The airremoval port 142 may feature a tethered cap 143 which can be moved toclose air removal port 142. The downspout assembly 115 can consist of alarge diameter funnel 117, an outflow tube 118, and an outlet port 116.The outflow tube 118 extends down, connecting the bottom of the largediameter funnel 117 to outlet port 116.

As best illustrated in FIGS. 10, 11 & 12, the blood filter system 100may contain a multi-stage sequential filter assembly 120 meant toachieve all the same principles of operation and advantages of use aspreviously described above for the multi-stage sequential filterassembly 60 of blood filter system 10.

As shown in FIG. 10, inlet port 112 with flared inlet channel 114 anddownspout assembly 115 are designed and positioned in blood filtersystem 100 so that they achieve all the same principles of operation andadvantages of use as previously described above for inlet port 32, inletchannel 33 and downspout assembly 34 of blood filter system 10.

As seen in FIG. 10, blood filter system 100 also features a unique upand down blood flow path meant to achieve all the same principles ofoperation and advantages of use as previously described above for bloodfilter system 10.

Also illustrated in FIGS. 10 & 11, the filter retaining ring 153positioned above filters 122, 128 & 134 comprise defined openings 150,154, 156 & 158 in fluid communication with the interior of filterhousing 110. The active air purge assembly 140 further comprises ahydrophobic filter 144 in fluid communication with defined openings 150,154, 156 & 158 of filter retaining ring 153, a one-way valve 146 influid communication with hydrophobic filter 144 and an air removal port142 and pressure monitoring port 148 in fluid communication with theone-way valve 146.

Defined openings 154, 156 & 158 of filter retaining ring 153 allow bloodcarrying air bubbles and debris to enter the active air purge assembly140 where they come in contact with hydrophobic filter 144 and are thenremoved.

The purge port 150 contains a micro-pore screen disk filter 152positioned just after defined opening 158 which allows filtered blood toleave the active air purge assembly 140 and rejoin with the blood flowexiting blood filter system 100 through downspout assembly 115. Thepurge port 150 may also comprise a small diameter opening which providesa restriction to blood flow out of active air purge assembly 140 toensure adequate time for air bubble removal through hydrophobic filter144. The purge port 150 may be adapted so that it is recessed within thefilter retaining ring 153 so as to keep its micro-pore screen diskfilter 152 submerged within the blood at all times.

The hydrophobic filter 144 is adapted so that free gasses and not theblood within the filter housing 110 comes in contact with the one-wayvalve 146. Air bubbles and debris within the blood flow which cannoteasily pass through the wetted pores of filter screens 124, 130 & 136are swept up along the outside proximal surface of angled filters 122,128 & 134 and directed into the active air purge assembly 140 throughdefined openings 154, 156 & 158 of filter retaining ring 153.Additionally, purge port 150 allows the negative pressure containedwithin a drainage circuit to be equally distributed throughout filterhousing 110 and active air purge assembly 140 below the hydrophobicfilter 144. This negative pressure augments the sweeping action createdby the angled filters within the blood flow by actively drawing bloodcontaining air bubbles and debris which cannot pass through the wettedpores up along the outside proximal surface of filters 122, 128 & 134through defined openings 154, 156 & 158 of filter retaining ring 153 andinto the active air purge assembly 140 where they come in contact withthe hydrophobic filter 144 and are removed. Air bubbles in contact withthe hydrophobic filter 144 may be absorbed passively or may be activelypulled from the blood using a suction source attached to the air removalport 142. The use of suction and the resulting negative pressure itcreates above hydrophobic filter 144 ensures an active and more rapidabsorption of air bubbles from the blood to further improve filterefficiency. Once passed the hydrophobic filter 144, free gases thencross the one-way valve 146 before being vented to the atmospherethrough air removal port 142. A pressure monitoring port 148 is used tokeep negative pressures within the active air purge assembly 140 at safelimits and within a user-defined range.

Moreover, blood filter system 100 uses all the same principles ofoperation and advantages of use to decrease the risk of reaching thebubble point pressure as previously described above for blood filtersystem 10. Also, blood filter system 100 incorporates the same designfeatures as blood filter system 10 so that the active air purge assembly140, downspout assembly 115 and hydrostatic pressure contained withinthe extracorporeal circuit work in unison as previously described aboveto prevent the blood filter system 100 from becoming de-primed.

Blood flow through filter system 100 passes through each filter stage122, 128 & 134 in sequence, multiplying the barrier to air bubble anddebris transfer to greatly improve blood filtration and filterefficiency. As long as the Bubble Point Pressure is not exceeded, thewetted pores of filter screens 124, 130 & 136 allow only blood to passthrough while preventing the passage of air bubbles and debris. Any airbubbles and debris within the blood are directed up along the outsideproximal surface of filter 122 through defined opening 154 of filterretaining ring 153 and into the active air purge assembly 140. In theevent that the Bubble Point Pressure is exceeded and air is ejectedacross the micro-pore filter screen 124, they are then directed up alongthe outside proximal surface of filter 128 and through defined opening156 of filter retaining ring 153 where they enter the active air purgeassembly 140 to be removed. If the Bubble Point Pressure is againexceeded at filter 128, they are then directed up along the outsideproximal surface of filter 134 and through defined opening 158 of filterretaining ring 153 then enter active air purge assembly 140 where theyare expelled.

Both blood filter systems 10 and 100 posses unique features thattogether comprise a major advancement in blood filtration forextracorporeal circulations over that of the prior art including asmaller micro-pore screen filter contact surface area, reduced totaldevice priming volume, unique shaped filter housing, unique up and downblood flow path, unique multi-stage sequential filter assembly, uniqueangled placement of micro-pore screen filters within the blood flow,unique sweeping action of blood flow on the micro-pore screen filters,reduced force of collision between air bubbles and angled screenfilters, unique active air purge assembly, unique method of utilizingsuction pressure to separate air bubbles from blood flow, uniquepressure relief valve, unique downspout assembly, unique method ofutilizing negative pressure within a venous drainage limb to augment airbubble and debris clearance and unique method of preventing the filterfrom becoming de-primed.

While the preferred embodiments of the blood filter system have beendescribed in detail, it should be apparent that modifications which fallwithin the true spirit and scope of the invention are possible. Withrespect to the above description, it is realized that the optimumrelationships for the parts of the invention including variations insize, materials, shape, form, function, manner of operation, assemblyand use are deemed readily apparent and obvious to one skilled in theart and that all equivalent relationships to those illustrated in thedrawings and described in the specification are intended to beencompassed by the present invention.

Therefore, the foregoing is to be considered only as illustrative of theprinciples and concepts of the present invention and that it is notdesired to limit the invention to the exact construction and operationas shown and described.

1. A conical filter housing comprising a purge port and an inlet andoutlet being adapted so that fluid passes from said inlet located at theouter edge of said conical filter housing base and rises up to thecenter of said conical filter housing where the fluid is then directeddown through said outlet away from said conical filter housing's top. 2.The blood filter system of claim 1 further comprising a multi-stagesequential filter assembly where: two or more micro-pore filters placedsequentially one after the other between said inlet and outlet of saidconical filter housing so that fluid must pass through each of saidmicro-pore filters in sequence; and each of said micro-pore filters ispositioned at an angle greater then 90 degrees to the fluid flow pathwithin said conical filter housing; and each of said micro-pore filtersattaches at its top to a filter retaining ring located below said purgeport so that each of said micro-pore filters has its proximal surface influid communication with defined openings within said filter retainingring; and said openings of said filter retaining ring are in fluidcommunication with said purge port; and a method to improve rate offiltration and decrease micro bubble generation within said conicalfilter housing and said method comprising the following steps where: (a)the force of the fluid flowing through said angled micro-pore filterswithin said conical filter housing creates a sweeping action which keepsthe proximal surface of each said micro-pore filter clean of air bubblesand debris; and (b) the angled placement of each said micro-pore filterwithin said conical filter housing is such that it reduces the force ofcollision between any air bubbles coming in contact with said micro-porefilter to prevent further fragmentation of air bubbles; and (c) thesequential placement of said micro-pore filters within said conicalfilter housing is adapted to allow increased filtration efficiency whileutilizing a decrease in total filter surface area.
 3. The blood filtersystem of claim 2 further comprising a flared inlet connected to saidinlet port and said conical filter housing upstream of said micro-porefilters and said flared inlet being adapted to decrease flow velocity offluid stream before entering said conical filter housing.
 4. The bloodfilter system of claim 3 further comprising an active air purge assemblylocated above said filter retaining ring; and said active air purgeassembly further comprising a hydrophobic filter in fluid communicationwith the interior of said conical filter housing; a one-way valve influid communication with said hydrophobic filter and the atmosphere; anair removal port and pressure monitoring port above said one-way valve;and said hydrophobic filter being adapted to allow free gasses and notfluid to travel to said one-way valve and out through said air removalport; and a method for monitoring and maintaining safe levels of saidsuction pressure attached to said air removal port and said methodcomprising the steps where: (a) a pressure monitoring device attached tosaid pressure monitoring port measures pressure above said hydrophobicfilter within said active air purge assembly; and (b) said suctionpressure attached to said air removal port can then be increased ordecreased to maintain safe levels of negative pressure above saidhydrophobic filter.
 5. The blood filter system of claim 4 furthercomprising a rising inner wall and downspout assembly located downstreamof said micro-pore filters to form in part a unique up and down fluidflow path through said conical filter housing; and said downspoutassembly being adapted to decrease fluid flow velocity below said activeair purge assembly; and a method of utilizing hydrostatic pressurecontained within said conical filter housing to keep said conical filterhousing from becoming de-primed while in use and said method comprisingthe following steps where: (a) said active air purge assembly locatedabove said downspout assembly is adapted so that it comprises a largerdiameter over that of said inlet port thereby acting as a pressurerelief valve; and (b) said downspout assembly comprises a chamber withinsaid conical filter housing and adapted so that it contains saidhydrostatic pressure within said conical filter housing; and (c) saidhydrostatic pressure contained within said downspout assembly prohibitsde-priming of said conical filter housing and further allows for theautomatic retrograde filling of the said conical filter housing.
 6. Theblood filter system of claim 5 further comprising a disk filter locatedin said downspout assembly and adapted so that said disk filter remainssubmerged within fluid at all times while in use.
 7. An alternateembodiment of the blood filter system of claim 1 wherein a cylindricalfilter housing comprising a filter retaining ring with purge port and aninlet and outlet is adapted so that fluid passes from said inlet locatedat the base of said cylindrical filter housing and rises up and thenback down through said outlet away from said cylindrical filterhousing's top.
 8. The blood filter system of claim 7 further comprisingsaid multi-stage sequential filter assembly; and said flared inletconnected to said inlet port and said cylindrical filter housingupstream of said micro-pore filters; and said active air purge assemblywith said air removal port and said pressure monitoring port; and saidactive air purge assembly is located above and in fluid communicationwith said filter retaining ring; and said rising inner wall and saiddownspout assembly located downstream of said micro-pore filters to formin part a unique up and down fluid flow path through said cylindricalfilter housing; and said disk filter located in said purge port of saidfilter retaining ring being adapted so that said disk filter remainssubmerged within fluid at all times while in use.
 9. The blood filtersystem of claim 8 further comprising a method for utilizing negativepressure contained within a fluid stream to improve filtrationefficiency and air bubble clearance and said method comprising the stepsof: (a) said filter retaining ring in fluid communication with saidactive air purge assembly is adapted to comprise said purge port andsaid defined openings above said micro-pore filters; and (b) said purgeport and said defined openings being adapted so that fluid may pass fromsaid cylindrical filter housing through said defined opening into saidactive air purge assembly and then back into said cylindrical filterhousing through said purge port; and (c) said purge port being adaptedso that negative pressure contained within said cylindrical filterhousing is also contained within said active air purge assembly; and (d)air bubbles and free gases entering said cylindrical filter housing andunable to pass through said micro-pore filters and are swept upwardsthrough said defined openings in said filter retaining ring by negativepressure contained within said active air purge assembly; and (e) airbubbles within active air purge assembly are then removed through saidhydrophobic filter said one-way valve and said air removal port; and (f)fluid within said active air purge assembly is drawn by negativepressure contained within said cylindrical filter housing through saidpurge port back into said cylindrical filter housing.
 10. The bloodfilter system of claim 9 further comprising a method for utilizingsuction pressure attached to said air removal port to actively pull airbubbles and free gas from the fluid stream and said method comprisingthe steps of: (a) suction pressure applied to said air removal portcreates negative pressure above said hydrophobic filter; and (b) airbubbles within said active air purge assembly and in fluid communicationwith said hydrophobic filter are actively drawn through hydrophobicfilter by negative pressure created above said hydrophobic filter; and(c) free gas is then pulled by said suction pressure applied to said airremoval port through said one-way valve and then vented out toatmosphere.
 11. The blood filter system of claim 10 further comprising amethod for monitoring and maintaining safe levels of said suctionpressure attached to said air removal port and said method comprisingthe steps where: (a) a pressure monitoring device attached to saidpressure monitoring port measures pressure above said hydrophobic filterwithin said active air purge assembly; and (b) said suction pressureattached to said air removal port can then be increased or decreased tomaintain safe levels of negative pressure above said hydrophobic filter.12. A method for removing free gas bubbles and debris from blood andsaid method comprising the steps where: (a) a blood filter systemcomprising a filter housing with purge port and adapted so that bloodflow must pass from said filter housing inlet port through a multi-stagesequential filter assembly and up along a rising inner wall and backdown through a downspout assembly and then out through an outlet portand; (b) said filter housing also being adapted so that air bubblesentering said filter housing must pass through said filter housing inletport and up along proximal surface of said multi-stage sequential filterassembly and through a filter retaining ring located above saidmulti-stage filter assembly and then out through said purge port locatedabove said filter retaining ring; (c) said filter housing being adaptedso that air bubbles entering said filter housing and that have passedthrough said multi-stage sequential filter assembly are then directed upto come in contact with an active air purge assembly; (d) a multi-stagesequential filter assembly within the said filter housing comprises atleast two said filters positioned at angles greater then 90 degrees tothe fluid flowing through said filter housing; (e) passing the bloodstream through multiple said filters positioned sequentially at anglesgreater then 90 degrees to blood flow within said filter housing; (f)angle of said filters creates a sweeping action of the blood flow on thesaid filters to remove air bubbles and debris from the proximal surfaceof said filters; (g) angle of said filters reduces force of collisionbetween air bubbles coming in contact with said filters to reduce microbubble generation; (h) angle of said filters directs free gas bubblesand debris up along the proximal surface of said filters toward saidpurge port; (i) a flared inlet adapted to decrease blood flow velocityand improve air bubble separation from said blood stream before enteringsaid filter housing; (j) said active air purge assembly located abovesaid multi-stage sequential filter assembly further comprises ahydrophobic filter in fluid communication with the interior of saidfilter housing, a one-way valve in fluid communication with saidhydrophobic filter and the atmosphere, an air removal port, a pressuremonitoring port and said hydrophobic filter being adapted to allow freegasses and not fluid to travel to said one-way valve and out throughsaid air removal port; (k) separating free gas bubbles from the bloodstream that have passed through said multi-stage sequential filterassembly using said hydrophobic filter; (l) directing free gas bubblesthat have passed through said hydrophobic filter through said one-wayvalve; (m) venting free gas bubbles that have passed through saidone-way valve to the atmosphere through air removal port; (n) monitoringpressure within said active air purge assembly above said hydrophobicfilter via said pressure monitoring port; (o) said rising inner wall andsaid downspout assembly adapted so that blood flow must follow a uniqueup and down flow path through said filter housing; (p) said downspoutassembly decreases blood flow velocity directly below said active airpurge assembly to direct buoyant air bubbles that have passed throughsaid multi-stage sequential filter assembly to come in contact with saidhydrophobic filter; (q) said downspout assembly further comprises a diskfilter to prevent air bubbles from passing through said outlet port; (r)said downspout assembly is also adapted to contain a hydrostaticpressure to prevent said filter housing from becoming de-primed while inuse; (s) said active air purge assembly further comprises a diameterlarger then said inlet port to act as a pressure relief valve;
 13. Themethod of claim 12 further comprising the step of connecting said bloodfilter system to an extracorporeal circuit so that blood containing airbubbles can be continuously removed form the blood stream and the newlyfiltered blood is continuously returned to a patient.